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Chrysoprase is a distinct gemstone quality variety of chalcedony quartz, a cryptocrystalline form of silicon dioxide. Chrysoprase is highly prized for its opalescent minty, apple-green color, which is especially unique and is owed to its distinctive coloring agent. Most green gemstones are colored by iron (tourmaline), chromium (emerald) or vanadium (tsavorite garnet), but chrysoprase derives its alluring color from nickel impurities, which form within otherwise colorless quartz crystal. Chrysoprase is considered to be one of the rarest and most valuable varieties of chalcedony quartz, second only to the rare green-blue gem silica, which is also known as 'chrysocolla chalcedony'.

The name 'chrysoprase' originates from the Greek words, 'chrusos' and 'prason', meaning 'gold' and 'leek', respectively; referring to its leek-green color and the presence of golden inclusions. Chrysoprase frequently occurs in quartz veins of nickel-bearing serpentine rocks and in weathered deposits of nickel ore materials. Chrysoprase, like all other varieties of cryptocrystalline quartz, is composed of crystals that are too fine to be seen as distinct particles, even under magnification. Unlike most chalcedony quartz varieties that are prized for their multi-colored patterns, chrysoprase is desired for its solid and vivid green color, which is reminiscent of the finest quality jade.